Editor has large margins when text is too long

Problem/Motivation

When enteric json into the Code mirror editor and the code is too long the edit view box becomes too wide and the text is thrown offscreen.

Steps to reproduce

After installing Code mirror create a new text format and set the editor to only use Code Mirror. They enter a json string that is very tall(I'm using one that's 68 lines tall)

Proposed resolution

Update the CSS so the editor always stays on the left no matter how much text is on screen.

Remaining tasks

User interface changes

API changes

Data model changes